ΔE 11.7, fair: the same colour family, but not a straight swap. Gnoll Brown is a little darker, cooler than Leather Brown.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 12). Gnoll Brown is a little darker, cooler than Leather Brown.
The same difference applies the other way round: Leather Brown is a little lighter, warmer.
ΔE is the colour difference between our two swatch estimates: under about 6 is close, over about 15 is loose. Real paints also differ in finish, coverage and how they thin, so test before you commit.
See Leather Brown on the colour wheel See Gnoll Brown on the colour wheel
All matches: Leather Brown equivalents · Gnoll Brown equivalents